Poxviruses

Question 1

genome type

Answer 1

dsDNA

Question 2

capsid structure

Answer 2

complex capsid - neither helical or icosahedral

Question 3

enveloped?

Answer 3

enveloped

Question 4

IMV vs EEV

Answer 4

IMV = intracellular mature virion
i. Released by lysis
ii. More common

EEV = extracellular enveloped virion
i. Wrapped in extra membranes from the golgi and exits via exocytosis = less deadly to cells = stealthy

Question 5

Where do poxviruses replicate and why is this important?

Answer 5

They replicate in the cytoplasm so they need viral associated enzymes for early transcription

Question 6

Do poxviruses do splicing?

Answer 6

No because they are not transcribed in the nucleus

Question 7

Viral associated enzymes

Answer 7

i. RNA pol
ii. Transcription factors
iii. 5’ mRNA capping enzyme
iv. Poly(A) pol

Question 8

Why is it good that the pox genome is gene-dense and massive?

Answer 8

Allows it to have genes that facilitate evading of restriction factors

Can have genes that modify cellular processes to benefit the virus, recruit dependency factors

Question 9

Know the difference between the central conserved and the terminal region of poxvirus genomes. What sort of genes are found in either? Why are terminal regions more variable?

Answer 9

Center = conserved = replication/assembly/surface proteins

Ends = encode species specific proteins = variable

Question 10

VAP and fusion?

Answer 10

H3 protein. Fusion can be pH dependent or independent

Question 11

host receptor

Answer 11

H3 protein binds hosts glycosaminoglycans (GAGs)

Question 12

early phase of life cycle

Answer 12

dsDNA released into the cytoplasm and early genes are transcribed and translated using viral polymerases

Question 13

intermediate phase of the life cycle

Answer 13

intermediate genes expressed

genomic dna replicated

Question 14

late phase of life cycle

Answer 14

i. structural proteins produced
ii. new viruses are made in cytoplasmic viral factories
iii. IMV released via lysis
iv. EEV released by exocytosis

Question 15

Poxviruses don’t fully expose themselves in the cytoplasm. How do they shield themselves from detection during transcription, replication, and assembly?

Answer 15

Cytoplasmic viral factories = “mini nuclei”

Organelles are derived from the ER

Question 16

Understand the pathogenesis of smallpox from how it enters the body to the development of rash. Which route of infection will lead to systemic disease? Which route is localized?

Answer 16

a. Aerosol/inhalation = more spread and systemic
b. Pus = less spread and localized

c. Primary site of infection = Macrophages in the respiratory mucosa
d. Primary viremia = Macrophages go to lymph nodes and virus enter blood
e. Secondary viremia = The macrophages of other lymphoid organs get infected
f. Endothelial infection = rash AFTER secondary viremia

Question 17

Can people be asymptomatic?

Answer 17

no

Question 18

Be familiar with at least three of the factors leading to smallpox eradication.

Answer 18

a. Humans are the only reservoir
b. Infection = visible symptoms
c. One serotype = antibodies for life

Question 19

Vaccine class of modern pox vaccines and which virus was it based off?

Answer 19

live attenuated

horse pox

Question 20

Consider the implications of smallpox as a biological weapon if it were released today. Should we destroy the remaining smallpox samples and be done with it for good?

Answer 20

a. No, who knows who has samples somewhere
b. It can survive in dead bodies
c. It can be recreated from its genetic information